Understanding errors from into_pyobject()

[CastilloDel]

Hello! I was migrating some code to a newer version. In some place, I was using .into_py(py) to convert a Rust type (that uses the [pyclass] attribute) to a Python type. I saw this was deprecated and I should use .into_pyobject(py) instead. However, it was a surprise to me to find out that this returned a Result instead of just Bound. I checked https://pyo3.rs/v0.23.3/conversions/traits.html, but couldn't find any explanation about what could fail.

TLDR: I would like to know if a struct that uses [pyclass] can really return an error when calling into_pyobject() and in which cases this could happen.

Thanks in advance!

[mejrs]

There are some cases where the conversion needs to import a type or call a python method, which can fail. Things like the date/time/hashmap etc related implementations are examples of conversions that can fail. On the other hand, if they cannot fail they use Infallible as the error type which means that on a new enough Rust you can write

let Ok(x) = y.into_pyobject();

[CastilloDel]

Thanks for the answer!